The present invention relates to an ion-producing apparatus for producing ions by applying an electron beam, and for emitting the ions thus produced.
An ion-producing apparatus of this type comprises a plasma-producing region, an accelerating cathode, an electron beam-accelerating region, an accelerating anode, and an ion-producing region, which are arranged in a line in this order. The apparatus further comprises a means for applying a potential to the target cathode, which is negative with respect to the potential of the accelerating anode, and an ion-extracting electrode for extracting cations or anions produced in the ion-producing region. In this apparatus, the accelerating anode attracts electrons from the plasma-producing region, which then rush into the ion-producing region, where they collide with the molecules of the inert gas (or the atoms of the metal vapor) present in the ion-producing region, thereby producing ions. These ions rush back to the accelerating cathode, and electrically neutralize the negative potential barrier formed in the vicinity of the outlet of the accelerating cathode. As a result, an electron beam having a large current, proportionate to the density of the plasma produced in the plasma-producing region, is applied to the ion-producing region. Hence, ions, the number of which is in proportion to the current value of the electron beam, are produced in the ion-producing region. These ions are attracted to the ion-extracting electrode, and are then emitted from the ion-producing region.
The apparatus described above is, however, rather complex in structure, is comparatively large, and cannot emit ions efficiently.